\documentclass{standalone}
\usepackage{tikz}
\usepackage{ctex,siunitx}
\setCJKmainfont{Noto Serif CJK SC}
\usepackage{tkz-euclide}
\usepackage{amsmath}
\usepackage{wasysym}
\usetikzlibrary{patterns, calc}
\usetikzlibrary {decorations.pathmorphing, decorations.pathreplacing, decorations.shapes,}
\begin{document}
\small
\begin{tikzpicture}[>=latex,scale=1]
  \draw[dash dot](-3,0)--(6,0);
  \draw [->, very thick](-2.5,0)--(-2.5,2)node[above]{蜡烛};
  \draw [dashed](-2.5,0)--(-2.5, -2);
  \draw [dashed](0,1.5)--(0, -.75);
  \draw [dashed](3.5,0)--(3.5, -1.5);
  \draw [dashed](5.5,0)--(5.5, -2);
  \draw [very thick](5.5,0)--(5.5, 3)node[right]{屏};
  \draw [<->](-2.5,.75)--node[fill=white]{$u_1$}(0,.75);
  \draw [<->](5.5,.75)--node[fill=white]{$v_1$}(0,.75);
  \draw [<->](3.5,-.5)--node[fill=white]{$d$}(0,-.5);
  \draw [<->](-2.5,-1)--node[fill=white]{$u_2$}(3.5,-1);
  \draw [<->](5.5,-1)--node[fill=white]{$v_2$}(3.5,-1);
  \draw [<->](-2.5,-1.5)--node[fill=white]{$L$}(5.5,-1.5);
  \fill (0,0) circle (1.5pt);  \fill (3.5,0) circle (1.5pt)node[above]{$B$};
  \node at (.2,0)[above]{$A$};
\end{tikzpicture}
\end{document}